JP2023003555A - Elastic wave device, filter, multiplexer, and wafer - Google Patents

Abstract

To provide an elastic wave device that can suppress spurious elements, and a filter including the elastic wave device.SOLUTION: An elastic wave device 100 includes: a supporting substrate 10; a piezoelectric layer 14 located on the supporting substrate 10; a pair of comb-like electrodes 22 located on the piezoelectric layer 14, the electrodes having a plurality of electrode fingers 23; and a plurality of layers 11a to 11d. The layers 11a to 11d include regions 15 and 16 alternately arranged in an X-direction between the supporting substrate 10 and the piezoelectric layer 14, the sound speed of a propagating bulk wave being different from one another. In each of the layers 11a to 11d, the regions 15 and 16 are provided from one surface to another surface facing each other in the thick direction. The regions 15, 16 in one of the layers 11a to 11d and the regions 15 and 16 in another of the layers next to the one layer have a boundary layer 11 in which the regions 15 in which the sound speeds of bulk waves are practically the same are displaced in the X-direction at least partially.SELECTED DRAWING: Figure 1

Description

The present invention relates to acoustic wave devices, filters, multiplexers, and wafers.

A surface acoustic wave resonator is known as an acoustic wave resonator used in communication devices such as smartphones. It is known to apply a piezoelectric layer forming a surface acoustic wave resonator to a supporting substrate. It is known to provide a temperature compensating layer between the supporting substrate and the piezoelectric layer (eg US Pat. It is known to provide a low acoustic velocity film having a lower acoustic velocity than the piezoelectric layer between the supporting substrate and the piezoelectric layer, and to provide a high acoustic velocity membrane having a higher acoustic velocity than the piezoelectric layer between the low acoustic velocity membrane and the supporting substrate (see, for example, Patent Documents 2).

JP 2019-201345 A JP 2015-115870 A

The invention described in Patent Document 2 suppresses spurious emissions by roughening the upper surface of the support substrate between the support substrate and the high acoustic velocity film. However, the upper surface of the support substrate needs to be processed to have a rough surface suitable for suppressing spurious emissions, which increases the manufacturing cost. Therefore, it is desired to suppress the spurious by other methods.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress spurious.

The present invention comprises a support substrate, a piezoelectric layer provided on the support substrate, a pair of comb-shaped electrodes provided on the piezoelectric layer and having a plurality of electrode fingers, and between the support substrate and the piezoelectric layer. A plurality of layers in which a plurality of regions having different sound velocities of propagating bulk waves are repeatedly arranged in a direction in which the plurality of electrode fingers are arranged are stacked, and in each of the plurality of layers, the plurality of regions are The plurality of regions of one layer and the plurality of regions of the other layer, which are provided from one surface to the other surface facing each other in the thickness direction, are at least partly bulk waves and an insulating layer in which regions having substantially the same sound velocity are arranged with a shift in the arrangement direction.

In the above configuration, each of the plurality of regions of the layer located closest to the piezoelectric layer among the plurality of layers is arranged in the arrangement direction of one electrode finger out of the plurality of electrode fingers. It can be configured such that they are repeatedly arranged in the arrangement direction so as to overlap the whole.

In the above structure, a temperature compensating layer is provided between the insulating layer and the piezoelectric layer and has a temperature coefficient of elastic constant whose sign is opposite to the sign of the temperature coefficient of the elastic constant of the piezoelectric layer. The distance from the surface of the layer on the insulating layer side to the surface of the piezoelectric layer on which the pair of comb-shaped electrodes is provided is 2λ or less, and the insulating layer has a sound velocity of a bulk wave propagating from the temperature compensating layer. The layer closest to the piezoelectric layer may be in contact with the temperature compensating layer.

In the above configuration, the length in the arrangement direction of each of the plurality of regions may be 0.5 times or more and 1 time or less the average pitch of the plurality of electrode fingers.

In the above configuration, the length in the thickness direction of each of the plurality of regions may be 0.5 times or more and 4 times or less the average pitch of the plurality of electrode fingers.

In the above configuration, the plurality of regions of the adjacent one layer have a phase difference of 0.5 times or more and 1 time or less of the average pitch of the plurality of electrode fingers with respect to the plurality of regions of the other layer. can be arranged repeatedly in the arrangement direction.

In the above configuration, boundaries between the plurality of regions may be inclined in a cross-sectional view parallel to the arrangement direction.

In the above structure, the plurality of regions are composed of a first region and a second region in which a bulk wave propagating from the first region has a lower acoustic velocity, and the second region has a bulk propagating bulk wave that propagates more slowly than the piezoelectric layer. The sound velocity of the wave is 1.01 times or more and 1.1 times or less, and the sound velocity of the propagating bulk wave in the first region is 1.2 times or more as compared to the second region. can.

The present invention is a filter including the acoustic wave device described above.

The present invention is a multiplexer including the filters described above.

The present invention provides a supporting substrate, a piezoelectric layer provided on the supporting substrate and being a rotated Y-cut X-propagating lithium tantalate layer or a rotated Y-cut lithium niobate layer, and provided between the supporting substrate and the piezoelectric layer. and a plurality of layers in which a plurality of regions having different sound velocities of propagating bulk waves are repeatedly arranged side by side in the X-axis direction of the crystal orientation of the piezoelectric layer, and the plurality of regions in each of the plurality of layers are provided from one surface to the other surface facing each other in the thickness direction, and the plurality of regions of one layer and the plurality of regions of the other layer of the plurality of layers are at least partially bulk and an insulating layer in which regions having substantially the same wave speed of sound are arranged in an offset manner in the X-axis direction.

According to the present invention, spurious can be suppressed.

FIG. 1(a) is a plan view of an acoustic wave device according to Example 1, and FIG. 1(b) is a cross-sectional view. 2A to 2D are cross-sectional views (part 1) showing the method of manufacturing the acoustic wave device according to the first embodiment. 3A to 3C are cross-sectional views (part 2) showing the method of manufacturing the acoustic wave device according to the first embodiment. FIGS. 4A to 4C are sectional views of models A, B, and C used in the first simulation. FIG. 5(a) is the simulation result of the admittance |Y| of the model C, and FIG. 5(b) is the simulation result of the admittance |Y| of the models A to C in the frequency range of 3000 MHz to 4500 MHz. FIGS. 6A to 6C are sectional views of models C, D, and E used in the second simulation. FIG. 7(a) is the simulation result of the admittance |Y| of the models C and D, and FIG. 7(b) is the simulation result of the admittance |Y| of the models C to E in the frequency range of 3000 MHz to 4500 MHz. . 8A and 8B are sectional views of models F and G used in the third simulation. FIG. 9(a) is the simulation result of the admittance |Y| of the models F and G, and FIG. 9(b) is the simulation result of the admittance |Y| . FIGS. 10(a) to 10(g) are sectional views of models E and H to M used in the fourth simulation. 11(a) to 11(d) are simulation results of admittance |Y| of model A, model E, and models H to J. FIG. 12(a) to 12(c) are simulation results of the admittance |Y| of the model A and the models K to M. FIG. FIG. 13 is a graph showing the relationship between the Z-direction length of a region in each layer constituting the boundary layer and high-frequency spurious. 14(a) to 14(d) are simulation results (part 1) of the admittance |Y| when the density of the region of the model F is changed. FIGS. 15(a) to 15(c) are simulation results (part 2) of the admittance |Y| when the density of the region of the model F is changed. FIGS. 16(a) and 16(b) are graphs showing the relationship between the density of regions in each layer constituting the boundary layer or the speed of sound and the high-frequency spurious. 17 is a cross-sectional view of an acoustic wave device according to Modification 1 of Embodiment 1. FIG. FIG. 18 is a circuit diagram of a filter according to Example 2. FIG. FIG. 19 is a block diagram of a duplexer according to the third embodiment; FIG. 20(a) is a plan view of a wafer according to Example 4, and FIG. 20(b) is a cross-sectional view.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1A is a plan view of the acoustic wave device 100 according to the first embodiment, and FIG. 1B is a cross-sectional view of the acoustic wave device 100 according to the first embodiment. The arrangement direction of the electrode fingers 23 is the X direction, the extending direction of the electrode fingers 23 is the Y direction, and the stacking direction (thickness direction) of the support substrate 10 and the piezoelectric layer 14 is the Z direction. The X-direction, Y-direction, and Z-direction do not necessarily correspond to the X-axis direction and Y-axis direction of the crystal orientation of the piezoelectric layer 14 . If the piezoelectric layer 14 is a rotated Y-cut X-propagation, the X-direction is the X-axis direction of the crystal orientation.

As shown in FIGS. 1A and 1B, an acoustic wave device 100 has a piezoelectric layer 14 on a support substrate 10 . A temperature compensation layer 12 is provided between the support substrate 10 and the piezoelectric layer 14 . A boundary layer 11 is provided between the temperature compensation layer 12 and the support substrate 10 . A bonding layer 13 is provided between the temperature compensation layer 12 and the piezoelectric layer 14 . Note that the bonding layer 13 may not be provided. The interface between the support substrate 10 and the boundary layer 11 is a flat surface, and the interface between the boundary layer 11 and the temperature compensation layer 12 is a flat surface. Further, the interface between the temperature compensation layer 12 and the piezoelectric layer 14 or the bonding layer 13 is also a flat surface. The thicknesses of the boundary layer 11, the temperature compensation layer 12, the bonding layer 13, and the piezoelectric layer 14 are T1, T2, T3, and T4, respectively.

The boundary layer 11 is formed by laminating a plurality of layers 11a, 11b, 11c, and 11d. The interfaces between the layers 11a-11d are flat surfaces. The multiple layers 11a-11d have multiple regions 15 and 16 in which the propagating bulk waves have different acoustic velocities. The regions 15 and 16 are provided from one surface to the other surface facing each other in the Z direction in each of the layers 11a to 11d, and are alternately arranged in the X direction. Adjacent layers among the plurality of layers 11a to 11d are arranged such that regions 15 and/or regions 16 in which bulk wave sound velocities are substantially the same are shifted in the X direction at least in part.

An elastic wave resonator 20 is provided on the piezoelectric layer 14 . The elastic wave resonator 20 has an IDT (Interdigital Transducer) 21 and a reflector 25 . The reflectors 25 are provided on both sides of the IDT 21 in the X direction. The IDT 21 and reflector 25 are formed by a metal film 27 on the piezoelectric layer 14 .

The IDT 21 includes a pair of comb electrodes 22 facing each other. The comb-shaped electrode 22 includes a plurality of electrode fingers 23 and a bus bar 24 to which the plurality of electrode fingers 23 are connected. A crossing region 26 is a region where the electrode fingers 23 of the pair of comb-shaped electrodes 22 intersect. The length of the intersection region 26 is the aperture length. The pair of comb-shaped electrodes 22 are provided facing each other so that the electrode fingers 23 are substantially staggered in at least a portion of the intersecting region 26 . Elastic waves excited by the plurality of electrode fingers 23 in the intersecting region 26 mainly propagate in the X direction. The pitch of one comb-shaped electrode 22 of the pair of comb-shaped electrodes 22 is approximately the wavelength λ of the elastic wave. Assuming that the pitch of the plurality of electrode fingers 23 is D, approximately twice the pitch D is the wavelength λ of the elastic wave. The reflector 25 reflects the acoustic waves (surface acoustic waves) excited by the electrode fingers 23 of the IDT 21 . This confines the acoustic wave within the intersection region 26 of the IDT 21 .

The piezoelectric layer 14 is, for example, a single-crystal lithium tantalate layer or a single-crystal lithium niobate layer, such as a rotated Y-cut X-propagating lithium tantalate layer or a rotated Y-cut X-propagating lithium niobate layer.

The support substrate 10 is, for example, a sapphire substrate, a silicon substrate, a spinel substrate, a quartz substrate, a crystal substrate, an alumina substrate, or a silicon carbide substrate. The sapphire substrate is a monocrystalline Al ₂ O ₃ substrate, the silicon substrate is a monocrystalline or polycrystalline silicon substrate, and the spinel substrate is a polycrystalline MgAl ₂ O ₄ substrate. The quartz substrate is an amorphous _SiO2 substrate, the quartz substrate is a monocrystalline _SiO2 substrate, and the silicon carbide substrate is a polycrystalline or monocrystalline SiC substrate. The X-direction linear expansion coefficient of the support substrate 10 is smaller than the X-direction linear expansion coefficient of the piezoelectric layer 14 . Thereby, the frequency temperature dependence of the acoustic wave resonator 20 can be reduced.

The temperature-compensating layer 12 has a temperature coefficient of elastic constant of opposite sign to the temperature coefficient of elastic constant of the piezoelectric layer 14 . For example, the piezoelectric layer 14 has a negative temperature coefficient of elastic constant, and the temperature compensating layer 12 has a positive temperature coefficient of elastic constant. The temperature compensation layer 12 is, for example, a silicon oxide (SiO ₂ ) layer containing no additive or an additive element such as fluorine, and is, for example, an amorphous layer. By providing the temperature compensation layer 12, the frequency temperature coefficient of the acoustic wave resonator 20 can be reduced. When the temperature compensating layer 12 is mainly composed of silicon oxide, the acoustic velocity of bulk waves propagating through the temperature compensating layer 12 is slower than the acoustic velocity of bulk waves propagating through the piezoelectric layer 14 . Having silicon oxide as the main component means that the total of oxygen and silicon is 50 atomic % or more, and may be 80 atomic % or more. Each of oxygen and silicon is 10 at % or more, and may be 20 at % or more.

The acoustic velocity of the bulk wave propagating through the boundary layer 11 is higher than the acoustic velocity of the bulk wave propagating through the temperature compensating layer 12 . That is, both of the regions 15 and 16 of the plurality of layers 11 a to 11 d that make up the boundary layer 11 have a faster bulk wave speed than the temperature compensating layer 12 . This confines the energy of the main response within the piezoelectric layer 14 and temperature compensating layer 12 . The boundary layer 11 is for example polycrystalline or amorphous, for example an aluminum oxide layer, a silicon layer, an aluminum nitride layer, a silicon nitride layer or a silicon carbide layer. A plurality of layers of different materials may be provided as the boundary layer 11 .

The regions 15 and 16 provided in the plurality of layers 11a to 11d forming the boundary layer 11 may be made of different materials so that the propagating bulk waves have different sound velocities, or may be made of the same material but different densities. good too. Also, regions 15 and 16 may differ in the speed of sound of bulk waves propagating by other methods. At least one of the regions 15 and 16 may have a bulk wave with a faster acoustic velocity than the temperature compensation layer 12 .

The acoustic velocity of the bulk wave propagating through the support substrate 10 is faster than the acoustic velocity of the bulk wave propagating through the boundary layer 11, and is preferably at least 1.1 times the acoustic velocity of the bulk wave propagating through the boundary layer 11, for example. The acoustic velocity of the bulk wave propagating through the support substrate 10 is preferably 2.0 times or less the acoustic velocity of the bulk wave propagating through the boundary layer 11 .

The acoustic velocity of the bulk wave propagating through the temperature compensating layer 12 may be faster than the acoustic velocity of the bulk wave propagating through the piezoelectric layer 14. It is preferably slower than the speed of sound of the propagating bulk wave, preferably 0.99 times or less. If the acoustic velocity of the bulk wave propagating through the temperature compensating layer 12 becomes too slow, it becomes difficult for the elastic wave to exist in the piezoelectric layer 14 . It is preferably at least 0.9 times the speed of sound of bulk waves.

The acoustic velocity of the bulk wave propagating through the bonding layer 13 is faster than the acoustic velocity of the bulk wave propagating through the temperature compensation layer 12 . The bonding layer 13 is, for example, polycrystalline or amorphous, such as an aluminum oxide layer, a silicon layer, an aluminum nitride layer, a silicon nitride layer, or a silicon carbide layer. The acoustic velocity of the bulk wave propagating through the boundary layer 11 and the bonding layer 13 is preferably higher than the acoustic velocity of the bulk wave propagating through the piezoelectric layer 14 .

The metal film 27 is a film mainly composed of aluminum, copper, or molybdenum, for example. An adhesion film such as a titanium film or a chromium film may be provided between the electrode fingers 23 and the piezoelectric layer 14 . The adhesion film is thinner than the electrode fingers 23 . An insulating film may be provided to cover the electrode fingers 23 . The insulating film may function as a protective film and a temperature compensating film.

When the IDT 21 excites surface acoustic waves, which are the main mode, in the piezoelectric layer 14, it also excites unnecessary waves such as bulk waves. The range where the energy of the surface acoustic wave exists is from the upper surface of the piezoelectric layer 14 to a depth of about 2λ, and particularly from the upper surface of the piezoelectric layer 14 to λ. On the other hand, unwanted waves such as bulk waves exist from the upper surface of the piezoelectric layer 14 to 10λ or more. If the bulk wave is reflected on the upper surface of the support substrate 10 and returns to the IDT 21, it causes spurious.

In order to suppress spurious, it has been proposed to scatter bulk waves by forming unevenness on the upper surface of the support substrate 10 . However, if an attempt is made to form unevenness suitable for scattering bulk waves on the upper surface of the support substrate 10, the manufacturing cost will increase. Therefore, in Example 1, instead of forming unevenness on the upper surface of the support substrate 10, the boundary layer 11 is formed of a plurality of layers 11a to 11d. Details of this point will be described later.

[Production method]
2A to 3C are cross-sectional views showing the method of manufacturing the acoustic wave device 100 according to the first embodiment. The manufacturing method shown in FIGS. 2A to 3C is performed in a wafer state, and finally the acoustic wave device 100 is formed by singulating the wafer. Although a plurality of acoustic wave devices 100 are formed on the wafer, only one acoustic wave device is shown in FIGS. 2(a) to 3(c).

As shown in FIG. 2A, a wafer-like support substrate 10 having a flat surface is prepared. The arithmetic mean roughness Ra of the surface of the support substrate 10 is, for example, 1 nm or less. An insulating film 15a is formed on the support substrate 10 by, for example, sputtering or CVD (Chemical Vapor Deposition), and then the insulating film 15a is removed by, for example, etching to form a patterned insulating film 15a. Note that the insulating film 15a may be formed by, for example, a lift-off method.

As shown in FIG. 2B, an insulating film 16a is formed on the supporting substrate 10 by, for example, sputtering or CVD, the sound velocity of a bulk wave propagating from the insulating film 15a being different from that of the insulating film 16a. The insulating films 15a and 16a may be made of different materials so that the propagating bulk waves have different sonic velocities. may be different, or the sound velocities of propagating bulk waves may be different in other ways. After that, the insulating film 16a is polished by, for example, CMP (Chemical Mechanical Polishing) until the insulating film 15a is exposed. Thereby, a layer 11a having a region 15 made of the insulating film 15a and a region 16 made of the insulating film 16a is formed.

As shown in FIG. 2C, after forming a resist pattern 90 on the layer 11a, an insulating film 16a is formed by sputtering or CVD, for example.

As shown in FIG. 2D, after removing the resist pattern 90, an insulating film 15a is formed on the layer 11a by sputtering or CVD, for example. Thereafter, the insulating film 15a is polished by, eg, CMP until the insulating film 16a is exposed. Thus, a layer 11b having a region 15 made of the insulating film 15a and a region 16 made of the insulating film 16a is formed.

As shown in FIG. 3(a), layers 11c and 11d are formed by repeating steps similar to those shown in FIGS. 2(c) and 2(d). As a result, a boundary layer 11 consisting of layers 11a to 11d is formed. After that, the temperature compensation layer 12 is formed on the boundary layer 11 by sputtering or CVD, for example.

As shown in FIG. 3B, the piezoelectric substrate 17 is bonded to the upper surface of the temperature compensation layer 12 via the bonding layer 13 . The temperature compensating layer 12 and the piezoelectric substrate 17 may be bonded without the bonding layer 13 interposed therebetween. A surface activation method, for example, is used for bonding.

As shown in FIG. 3C, the upper surface of the piezoelectric substrate 17 is polished using, for example, the CMP method to form a thin piezoelectric layer 14 . After that, the elastic wave resonator 20 made of the metal film 27 is formed on the upper surface of the piezoelectric layer 14 . Finally, the acoustic wave device 100 is formed by singulating the wafer.

[First simulation]
A first simulation for evaluating spurious will be described. The first simulation was performed for models A, B, and C having different structures of the boundary layers 11 to simulate the admittance of each model. Simulation conditions common to Models A, B, and C are as follows. The regions 15 and 16 of the boundary layer 11 have different densities of materials to make different sound velocities of propagating bulk waves. Regions 15 and 16 are provided throughout intersection region 26 in the manner shown in the figures to be described later. The following simulation conditions are common to the second to fifth simulations described later.
Elastic wave wavelength λ: 1.5 μm
Support substrate 10: sapphire substrate Boundary layer 11: Aluminum oxide layer with a thickness of 4λ Region 15 of the boundary layer ¹¹ : Aluminum oxide with a density of 3150 kg/m3 Region 16 of the boundary layer ¹¹ : Aluminum oxide with a density of 4500 kg/m3 Temperature compensation layer 12: Silicon oxide layer with a thickness of 0.2λ Piezoelectric layer 14: 42° Y-cut X-propagation lithium tantalate layer with a thickness of 0.3λ Electrode fingers 23: Provided on a titanium film with a thickness of 60 nm Laminated film of aluminum films having a thickness of 90 nm Logarithm of electrode fingers 23: 1 pair Duty ratio: 50%
Aperture length: λ/32

FIGS. 4A to 4C are sectional views of models A, B, and C used in the first simulation. 4(a) to 4(c), for clarity of illustration, the support substrate 10, the temperature compensation layer 12, the piezoelectric layer 14, and the electrode fingers 23 are omitted from hatching, and the boundary layer 11 , only the region 16 is hatched, and the hatching of the region 15 is omitted (the same applies to similar figures below).

As shown in FIG. 4( a ), model A uses the entire boundary layer 11 as region 15 . That is, the entire boundary layer 11 is made of aluminum oxide with a density of 3150 kg/m ³ . As described above, the model A is a model corresponding to the comparative example because the boundary layer 11 does not include a plurality of layers having the regions 15 and 16 .

As shown in FIG. 4(b), model B divides the boundary layer 11 into two in the X direction under the pair of electrode fingers 23 ^, one of which is a region 15 made of aluminum oxide with a density of 3150 kg/m3. and the other was a region 16 made of aluminum oxide with a density of 4500 kg/m ³ . That is, it is assumed that the boundary layer 11 is composed of one layer 11a having regions 15 and 16 arranged in the X direction. In model B, the length of the regions 15 and 16 in the Z direction is 4λ and the length in the X direction is 0.5λ. As described above, the model B is a model corresponding to the comparative example because the boundary layer 11 does not include a plurality of layers having the regions 15 and 16 .

As shown in FIG. 4(c), the model C divides the boundary layer 11 into two in the Z direction and the X direction under the pair of electrode fingers 23, and divides the four regions into +Z and +X regions and The region located at −Z and −X is the region 15 made of aluminum oxide with a density of 3150 kg/m ³ , and the region located at +Z and −X and the region located at −Z and +X have a density of 4500 kg/m ³ A region 16 made of aluminum oxide was used. That is, it is assumed that the boundary layer 11 is formed by laminating two layers 11a and 11b each having a region 15 and a region 16 arranged in the X direction. The region 15 of the layer 11a and the region 15 of the layer 11b are shifted in the X direction, and the region 16 of the layer 11a and the region 16 of the layer 11b are shifted in the X direction. In model C, regions 15 and 16 of each of layers 11a and 11b have a length of 2λ in the Z direction and a length of 0.5λ in the X direction. Thus, model C is a model corresponding to the example.

FIG. 5(a) is the simulation result of the admittance |Y| of the model C, and FIG. 5(b) is the simulation result of the admittance |Y| of the models A to C in the frequency range of 3000 MHz to 4500 MHz. As shown in FIGS. 5( a ) and 5 ( b ), model C resulted in suppression of high-frequency spurious compared to models A and B. FIG. The reason why high-frequency spurious is suppressed in model C is considered as follows. In the boundary layer 11 of model C, two layers 11a and 11b are laminated in which regions 15 and 16 having different sound velocities of propagating bulk waves are arranged in the X direction. The region 15 of the layer 11a and the region 15 of the layer 11b are shifted in the X direction, and the region 16 of the layer 11a and the region 16 of the layer 11b are shifted in the X direction. As a result, the bulk waves that have passed through the temperature compensating layer 12 from the piezoelectric layer 14 and reached the boundary layer 11 are scattered by the regions 15 and 16 of the layers 11a and 11b, and as a result, the high frequency spurious is suppressed.

According to Example 1, as shown in FIG. 1B, a boundary layer 11 (insulating layer) is provided between the support substrate 10 and the piezoelectric layer 14 . The boundary layer 11 is formed by laminating a plurality of layers 11a to 11d in which a plurality of regions 15 and 16 having different sound velocities of propagating bulk waves are repeatedly arranged in the X direction. In each of the plurality of layers 11a to 11d, regions 15 and 16 are provided from one surface to the other surface facing each other in the Z direction. The regions 15 and 16 of one of the layers 11a to 11d and the regions 15 and 16 of the other layer adjacent to each other among the plurality of layers 11a to 11d have substantially the same bulk wave acoustic velocity in at least a part of the regions 15 and/or regions 16. They are displaced in the X direction. As a result, the bulk waves are scattered by the regions 15 and 16 of the layers 11a to 11d, thereby suppressing the spurious caused by the bulk waves. The fact that the sound velocities of the bulk waves are substantially the same means that they are allowed to differ to the extent of a manufacturing error.

In Example 1, from the viewpoint of suppressing spurious by scattering bulk waves, the regions 15 and 16 of one adjacent layer among the plurality of layers 11a to 11d and the regions 15 and 16 of the other layer are all It is preferable that the regions 15 and the regions 16 having substantially the same sound speed of the bulk wave are arranged with a shift in the X direction.

In terms of allowing the bulk wave to reach the boundary layer 11, the thickness T2 of the temperature compensating layer 12 is preferably 1.5 times (0.75λ) or less the average pitch D of the electrode fingers 23, and 1 time (0.5λ). The following are more preferred. From the point of exhibiting the temperature compensating function of the temperature compensating layer 12, the thickness T2 of the temperature compensating layer 12 is preferably 0.2 times (0.1λ) or more the average pitch D of the electrode fingers 23, and 0.4 times ( 0.2λ) or more is more preferable. The average pitch D of the electrode fingers 23 can be calculated by dividing the width of the IDT 21 in the X direction by the number of electrode fingers 23 .

The boundary layer 11 is not limited to the case where the four layers 11a to 11d are laminated, and may be the case where two or more layers are laminated. From the viewpoint of scattering bulk waves by the boundary layer 11, the number of laminated layers of the boundary layer 11 is preferably as large as possible, preferably 3 or more, more preferably 5 or more, and even more preferably 8 or more. In addition, if the thickness T1 of the boundary layer 11 is thin, spurious emissions increase. It is more preferably two times (λ) or more, and even more preferably four times (2λ) or more.

From the viewpoint of confining the surface acoustic wave energy in the piezoelectric layer 14 and the temperature compensating layer 12, the distance (T2+T3+T4) between the surface of the temperature compensating layer 12 on the boundary layer 11 side and the surface of the piezoelectric layer 14 on the comb electrode 22 side is , preferably four times (2λ) or less, more preferably three times (1.5λ) or less, the average pitch D of the electrode fingers 23 . From the viewpoint of allowing the energy of the surface acoustic wave to exist in the temperature compensation layer 12, the thickness T4 of the piezoelectric layer 14 is preferably two times (λ) or less the average pitch D of the electrode fingers 23, and is one time (0.5λ). The following are more preferred. If the piezoelectric layer 14 is too thin, it becomes difficult to excite the elastic wave. 0.4 times (0.2λ) or more is more preferable.

[Second simulation]
FIGS. 6A to 6C are sectional views of models C, D, and E used in the second simulation. Since model C in FIG. 6A has been described in the first simulation, description thereof is omitted here.

As shown in FIG. 6B, model D divides the boundary layer 11 into two in the Z direction and four in the X direction under the pair of electrode fingers 23. The two regions located at the ends on the −X side were designated as regions 15, and the two regions located in the center were designated as regions 16. FIG. Of the four regions on the −Z side, the two regions located in the center were designated as regions 15, and the two regions located at the ends of the +X side and the −X side were designated as regions 16. FIG.

As shown in FIG. 6(c), model E divides the boundary layer 11 into two in the Z direction and four in the X direction under the pair of electrode fingers 23. The two regions positioned were designated as regions 15, and the two regions positioned on the -X side were designated as regions 16. FIG. Of the four regions on the −Z side, the two regions located at the ends on the +X side and the −X side were designated as region 15 , and the two regions located in the center were designated as region 16 .

Thus, in all models C, D, and E, the boundary layer 11 is laminated with two layers 11a, 11b each having a region 15 and a region 16 aligned in the X direction, and a region 15 of the layer 11a and a region 15 of the layer 11b. The regions 15 are shifted in the X direction, and the region 16 of the layer 11a and the region 16 of the layer 11b are shifted in the X direction. In models C, D and E, regions 15 and 16 of each of layers 11a and 11b have a Z-direction length of 2λ and an X-direction length of 0.5λ.

In model C, the regions 15 and 16 of the layer 11a each overlap the entire X direction of one electrode finger 23, and the regions 15 and 16 of the layer 11b each overlap the entire X direction of the electrode finger 23. are placed overlapping each other. In model D, the region 15 of the layer 11a is provided so as to overlap each half of the two electrode fingers 23 in the X direction, and the region 16 is also provided so as to overlap half of the electrode fingers 23 . Similarly, the region 16 of the layer 11b is provided so as to overlap each half of the two electrode fingers 23 in the X direction, and the region 15 is also provided so as to overlap half of the electrode fingers 23 . In model E, the region 16 of the layer 11a is provided so as to overlap each half of the two electrode fingers 23 in the X direction, and the region 15 is also provided so as to overlap half of the electrode fingers 23 . The regions 15 and 16 of the layer 11b are each provided so as to overlap the entire X direction of one electrode finger 23 .

FIG. 7(a) is the simulation result of the admittance |Y| of the models C and D, and FIG. 7(b) is the simulation result of the admittance |Y| of the models C to E in the frequency range of 3000 MHz to 4500 MHz. . As shown in FIGS. 7(a) and 7(b), model C suppresses high-frequency spurious compared to models D and E, and model E suppresses high-frequency spurious compared to model D. .

From the results of the second simulation, in Example 1, the regions 15 and 16 of the layer 11d located closest to the piezoelectric layer 14 among the plurality of layers 11a to 11d forming the boundary layer 11 are It is preferable that they are arranged in the X direction so as to overlap the entire X direction of one electrode finger 23 . As a result, as in Models C and E, high-frequency spurious can be suppressed. Moreover, in Example 1, it is preferable that the layer 11 d is a layer in contact with the temperature compensating layer 12 . As a result, as in Models C and E, high-frequency spurious can be suppressed. Further, in Example 1, in all of the plurality of layers 11a to 11d forming the boundary layer 11, the regions 15 and 16 are aligned in the X direction so as to overlap the entire X direction of one electrode finger 23. preferably. As a result, as in model C, high-frequency spurious can be suppressed.

Further, as shown in FIG. 6A, in the model C, the regions 15 and 16 of the layer 11a are aligned with the regions 15 and 16 of the layer 11b shifted by 0.5λ in the X direction. As shown in FIG. 6C, in the model E, the regions 15 and 16 of the layer 11a are aligned with the regions 15 and 16 of the layer 11b shifted by 0.25λ in the X direction. As shown in FIG. 7(b), both models C and E suppress high-frequency spurious. Therefore, in Example 1, from the viewpoint of suppressing high-frequency spurious, the regions 15 and 16 of one of the layers 11a to 11d adjacent to each other are 0.25λ with respect to the regions 15 and 16 of the other layer. It is preferable that they are arranged in the X direction with a phase difference of 0.5λ or less. In other words, the regions 15 and 16 of one of the layers 11a to 11d adjacent to each other are 0.5 times or more the average pitch D of the electrode fingers 23 with respect to the regions 15 and 16 of the other layer. It is preferable that they are arranged in the X direction with a phase difference of 1 or less.

As shown in FIG. 7(b), model C suppresses high-frequency spurious compared to model E. As shown in FIG. Therefore, from the viewpoint of suppressing high frequency spurious, when the regions 15 and 16 of one adjacent layer are arranged with a phase difference of 0.3λ or more and 0.5λ or less with respect to the regions 15 and 16 of the other layer , more preferably lined up with a phase difference of 0.4λ or more and 0.5λ or less, and still more preferably lined up with a phase difference of 0.45λ or more and 0.5λ or less. In other words, the adjacent regions 15 and 16 of one layer are arranged with a phase difference of 0.6 to 1 times the average pitch D of the electrode fingers 23 with respect to the regions 15 and 16 of the other layer. More preferably, they are arranged with a phase difference of 0.8 times or more and 1 time or less, and even more preferably, they are arranged with a phase difference of 0.9 times or more and 1 time or less.

[Third simulation]

8A and 8B are sectional views of models F and G used in the third simulation. As shown in FIG. 8(a), the model F divides the boundary layer 11 into four in the Z direction and two in the X direction under a pair of electrode fingers 23. are arranged in a grid. Regions 15 and 16 of layers 11a to 11d are each provided so as to overlap one electrode finger 23 entirely. In model F, regions 15 and 16 of layers 11a-11d have a length in the Z direction of λ and a length in the X direction of 0.5λ.

As shown in FIG. 8B, the model G divides the boundary layer 11 into four regions under the pair of electrode fingers 23 in the Z direction and the X direction, respectively, and the regions 15 and 16 of the four layers 11a to 11d are lattices. placed in the shape of Regions 15 and 16 of layers 11a-11d each overlap half of one electrode finger 23. As shown in FIG. In model G, regions 15 and 16 of layers 11a-11d have a length in the Z direction of λ and a length in the X direction of 0.25λ.

FIG. 9(a) is the simulation result of the admittance |Y| of the models F and G, and FIG. 9(b) is the simulation result of the admittance |Y| . As shown in FIG. 9, the result of model F was that high-frequency spurious was suppressed more than model G.

From the third simulation result, in order to suppress high-frequency spurious in Example 1, the length in the X direction of the regions 15 and 16 of the layers 11a to 11d constituting the boundary layer 11 is 0.25λ or more and 0.5λ. The following is preferable, 0.3λ or more and 0.5λ or less is more preferable, and 0.4λ or more and 0.5λ or less is still more preferable. In other words, the length in the X direction of the regions 15 and 16 of the layers 11a to 11d constituting the boundary layer 11 is preferably 0.5 times or more and 1 time or less the average pitch D of the plurality of electrode fingers 23, and 0.6 It is more preferably 0.8 times or more and 1 time or less, and still more preferably 0.8 times or more and 1 time or less.

[Fourth simulation]

FIGS. 10(a) to 10(g) are sectional views of models E and H to M used in the fourth simulation. Model E in FIG. 10(a) has been described in the second simulation, so the description is omitted here.

In model E of FIG. 10(a), the boundary layer 11 has a two-layered structure, whereas in model H, the boundary layer 11 has a three-layered structure, as shown in FIG. 10(b). As shown in FIG. 10(c), the boundary layer 11 has a four-layer structure in model I, and as shown in FIG. 10(d), in model J, the boundary layer 11 has a six-layer structure. there is As shown in FIG. 10(e), the boundary layer 11 has a laminated structure of 10 layers in the model K, and as shown in FIG. 10(f), the boundary layer 11 has a laminated structure of 25 layers in the model L. As shown in FIG. 10(g), in the model M, the boundary layer 11 has a laminated structure of 50 layers. In model H, regions 15 and 16 of each layer have a length in the Z direction of 1.33λ and a length in the X direction of 0.5λ. In Model I, regions 15 and 16 of each layer have a length in the Z direction of 1λ and a length in the X direction of 0.5λ. In Model J, regions 15 and 16 of each layer have a length in the Z direction of 0.67λ and a length in the X direction of 0.5λ. In model K, regions 15 and 16 of each layer have a length in the Z direction of 0.4λ and a length in the X direction of 0.5λ. In model L, regions 15 and 16 of each layer have a length in the Z direction of 0.16λ and a length in the X direction of 0.5λ. In model M, regions 15 and 16 of each layer have a length in the Z direction of 0.08λ and a length in the X direction of 0.5λ.

11(a) to 11(d) are simulation results of the admittance |Y| of the models E and H to J. FIG. 12(a) to 12(c) are simulation results of the admittance |Y| of the models K to M. FIG. In FIGS. 11(a) to 11(d) and FIGS. 12(a) to 12(c), simulation results of the admittance |Y| of model A (see FIG. 4(a)) are also shown for comparison. ing. As shown in FIGS. 11(a) to 11(c) and FIGS. 12(a) to 12(c), models E and H to M resulted in more suppressed high-frequency spurious than model A.

FIG. 13 is a graph showing the relationship between the length in the Z direction of the regions 15 and 16 in each layer forming the boundary layer 11 and the high-frequency spurious. The horizontal axis of FIG. 13 is the length of the regions 15 and 16 in the Z direction. The vertical axis represents the difference |ΔY| between the maximum and minimum admittance values of high-frequency spurious. In FIG. 13, the results of Models E and H to M are indicated by white circles, and the results of Model A are indicated by black circles. As shown in FIG. 13, the result was that the high-frequency spurious was most suppressed when the length of the regions 15 and 16 in the Z direction was 1λ.

From the fourth simulation result, in order to suppress high frequency spurious in Example 1, the length in the Z direction of the regions 15 and 16 of the layers 11a to 11d constituting the boundary layer 11 should be 0.25λ or more and 2λ or less. It is preferably 0.5λ or more and 1.5λ or less, and still more preferably 0.8λ or more and 1.2λ or less. In other words, the length in the Z direction of the regions 15 and 16 of the layers 11a to 11d constituting the boundary layer 11 is preferably 0.5 times to 4 times the average pitch D of the plurality of electrode fingers 23, and 1 time or more. 3 times or less is more preferable, and 1.6 times or more and 2.4 times or less is even more preferable. Thereby, high frequency spurious can be suppressed.

[Fifth simulation]
In the fifth simulation, model F shown in FIG. 8(a) was used, and the admittance was simulated when the density of region 15 was fixed at 3150 kg/m ³ and the density of region 16 was varied.

FIGS. 14(a) to 14(d) and FIGS. 15(a) to 15(c) are simulation results of the admittance |Y| when the density of the region 16 of the model F is varied. 14(a), the density of the region 16 is 1500 kg/m3 ^, FIG.14(b) is 2000 kg/m3 ^, FIG.14(c) is 3000 kg/m3 ^, and FIG.14(d) is , 4000 kg/m ³ , FIG. 15(a) is 4500 kg/m ³ , FIG. 15(b) is 4873 kg/m ³ , and FIG. 15(c) is 6000 kg/m ³ . In FIGS. 14(a) to 14(d) and 15(a) to 15(c), simulation results of the admittance |Y| of model A (see FIG. 4(a)) are also shown for comparison. ing.

16(a) and 16(b) are graphs showing the relationship between the density or sound velocity of the region 16 in each layer forming the boundary layer 11 and the high-frequency spurious. The horizontal axis of FIG. 16(a) is the density of the region 16, and the horizontal axis of FIG. 16(b) is the speed of sound of the region 16. The vertical axis of FIGS. 16(a) and 16(b) is the difference |ΔY| between the maximum and minimum admittance values in high-frequency spurious. In FIGS. 16(a) and 16(b), the results of Model F, in which the density (sound speed) of the region 16 is changed, are shown by white circles, and the results of Model A are shown by black circles.

As shown in FIGS. 14(a) to 14(d), 15(a) to 15(c), and 16(a) and 16(b), the density of region 16 is 1500 kg/m ³ . In all cases of shaking in the range of ~6000 kg/m ³ , the result was that high-frequency spurious was suppressed. From this, it was confirmed that if the sound velocities of the bulk waves in the regions 15 and 16 are different, the spurious can be suppressed regardless of the difference in sound velocities.

The acoustic velocity of the bulk wave propagating through the piezoelectric layer 14, which is the rotated Y-cut X-propagating lithium tantalate layer, is 3750 m/s, and the acoustic velocity of the bulk wave propagating through the temperature compensation layer 12, which is the silicon oxide layer, is 3684 m/s. . The sound velocity of a bulk wave propagating in the region 15 made of aluminum oxide with a density of 3150 kg/m ³ is 4582 m/s. As shown in FIG. 16B, when the region 16 has a bulk wave sound velocity close to that of the piezoelectric layer 14 and the temperature compensation layer 12 and the region 15 has a bulk wave sound speed higher than that of the region 16, the effect of suppressing high frequency spurious is is large. Therefore, in Example 1, when the layers 11a to 11d constituting the boundary layer 11 are composed of the region 15 and the region 16 in which the bulk wave propagating from the region 15 has a lower acoustic velocity, the region 16 is larger than the piezoelectric layer 14. The sound velocity of the bulk wave is preferably 1.01 times or more and 1.1 times or less, more preferably 1.01 times or more and 1.08 times or less, and 1.01 times or more and 1.05 times or less. is more preferred. The acoustic velocity of the bulk wave in the region 15 is preferably 1.2 times or more, more preferably 1.25 times or more, and still more preferably 1.3 times or more as compared to the region 16 . Thereby, spurious can be effectively suppressed.

If the acoustic velocity of the bulk wave propagating through the boundary layer 11 is too fast, the bulk wave is likely to be reflected at the interface between the boundary layer 11 and the temperature compensation layer 12. Therefore, the acoustic velocity of the bulk wave propagating through the boundary layer 11 is equal to that of the temperature compensation layer. It is preferably 2.0 times or less, more preferably 1.5 times or less, the sound velocity of a bulk wave propagating through 12.

[Modification]
17 is a cross-sectional view of an acoustic wave device 110 according to Modification 1 of Embodiment 1. FIG. As shown in FIG. 17, in acoustic wave device 110, regions 15 and 16 of a plurality of layers 11a to 11d forming boundary layer 11 have inclined side surfaces when viewed in cross section. The tilt angle θ is, for example, 40° to 89°. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

As in Modification 1 of Embodiment 1, the boundary between the regions 15 and 16 may be slanted in a cross-sectional view parallel to the X direction. As a result, bulk waves can be effectively scattered, and the effect of suppressing spurious emissions is increased.

In Example 1 and its modification example, the plurality of layers 11a to 11d has two regions 15 and 16 in which the propagating bulk waves have different sound velocities. It may be a case of having a plurality of areas of one or more. In this case, the plurality of regions of three or more in each of the plurality of layers 11a to 11d are arranged repeatedly in the X direction, and among the plurality of layers 11a to 11d, the plurality of regions of one adjacent layer and the plurality of regions of the other layer. In at least a part of the region where the sound speed of the bulk wave is substantially the same, the region is shifted in the X direction.

In the first embodiment and its modification, the case where the temperature compensating layer 12 is provided between the boundary layer 11 and the piezoelectric layer 14 is shown as an example, but the temperature compensating layer 12 may not be provided. However, the temperature compensation layer 12 is preferably provided in order to reduce the frequency temperature coefficient of the elastic wave resonator 20 .

FIG. 18 is a circuit diagram of the filter 200 according to the second embodiment. As shown in FIG. 18, a filter 200 has one or more series resonators S1 to S4 connected in series between an input terminal Tin and an output terminal Tout, and one or more parallel resonators P1 to P3. connected in parallel. At least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P3 can use the elastic wave device according to the first embodiment and its modifications. The number of resonators of the ladder-type filter and the like can be set as appropriate. The filter may be a multimode filter.

FIG. 19 is a block diagram of a duplexer 300 according to the third embodiment. As shown in FIG. 19, the duplexer 300 has the transmission filter 30 connected between the common terminal Ant and the transmission terminal Tx, and the reception filter 32 connected between the common terminal Ant and the reception terminal Rx. The transmission filter 30 allows the signal in the transmission band among the high-frequency signals input from the transmission terminal Tx to pass through the common terminal Ant as the transmission signal, and suppresses the signals of other frequencies. The reception filter 32 allows signals in the reception band among the high-frequency signals input from the common terminal Ant to pass through the reception terminal Rx as reception signals, and suppresses signals of other frequencies. At least one of the transmission filter 30 and the reception filter 32 can be the filter of the second embodiment. Although a duplexer is shown as an example of a multiplexer, a triplexer, a quadplexer, or the like may be used.

20A is a plan view of the wafer 400 according to Example 4, and FIG. 20B is a cross-sectional view of the wafer 400 according to Example 4. FIG. As shown in FIGS. 20( a ) and 20 ( b ), the wafer 400 has the piezoelectric layer 14 provided on the support substrate 10 . A temperature compensation layer 12 is provided between the support substrate 10 and the piezoelectric layer 14 . A boundary layer 11 is provided between the temperature compensation layer 12 and the support substrate 10 . Although the bonding layer 13 is provided between the temperature compensating layer 12 and the piezoelectric layer 14, the bonding layer 13 may not be provided.

The piezoelectric layer 14 is a rotated Y-cut X-propagating lithium tantalate layer or a rotated Y-cut X-propagating lithium niobate layer. The X-axis direction of the crystal orientation of the piezoelectric layer 14 is defined as the X-direction. The stacking direction (thickness direction) of the support substrate 10 and the piezoelectric layer 14 is defined as the Z direction. A direction perpendicular to the X direction and the Z direction is defined as the Y direction. Note that the supporting substrate 10, the boundary layer 11, the temperature compensating layer 12, and the bonding layer 13 are formed of the materials shown in the first embodiment.

The boundary layer 11 is formed by laminating a plurality of layers 11a to 11d. The multiple layers 11a-11d have multiple regions 15 and 16 in which the propagating bulk waves have different acoustic velocities. The regions 15 and 16 are provided from one surface to the other surface facing each other in the Z direction in each of the layers 11a to 11d, and are alternately arranged in the X direction. Adjacent layers among the plurality of layers 11a to 11d are arranged such that regions 15 and/or regions 16 in which bulk wave sound velocities are substantially the same are shifted in the X direction at least in part.

According to Example 4, the wafer 400 includes a support substrate 10, a piezoelectric layer 14 provided on the support substrate 10 and being a rotated Y-cut X-propagating lithium tantalate layer or a rotated Y-cut lithium niobate layer, and a support substrate. and a boundary layer 11 (insulating layer) provided between 10 and the piezoelectric layer 14 . The boundary layer 11 is formed by laminating a plurality of layers 11a to 11d in which a plurality of regions 15 and 16 having different sound velocities of propagating bulk waves are repeatedly arranged in the X direction. In each of the plurality of layers 11a to 11d, regions 15 and 16 are provided from one surface to the other surface facing each other in the Z direction. The regions 15 and 16 of one of the layers 11a to 11d and the regions 15 and 16 of the other layer adjacent to each other among the plurality of layers 11a to 11d have substantially the same bulk wave acoustic velocity in at least a part of the regions 15 and/or regions 16. They are displaced in the X direction. Thus, the layer structure of the wafer 400 is similar to the layer structure from the support substrate 10 to the piezoelectric layer 14 of the acoustic wave device 100 of the first embodiment. Therefore, by using the wafer 400 and forming an acoustic wave resonator on the piezoelectric layer 14, an acoustic wave device with suppressed spurious can be obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the scope of claims. Change is possible.

REFERENCE SIGNS LIST 10 support substrate 11 boundary layer 11a to 11d layer 12 temperature compensation layer 13 bonding layer 14 piezoelectric layer 15, 16 regions 15a, 16a insulating film 17 piezoelectric substrate 20 elastic wave resonator 21 IDT
22 Comb-shaped electrode 23 Electrode finger 24 Bus bar 25 Reflector 26 Intersection area 27 Metal film 30 Transmission filter 32 Reception filter 100, 110 Acoustic wave device 200 Filter 300 Duplexer 400 Wafer

Claims (11)

a support substrate;
a piezoelectric layer provided on the support substrate;
a pair of comb-shaped electrodes provided on the piezoelectric layer and having a plurality of electrode fingers;
a plurality of layers provided between the support substrate and the piezoelectric layer, in which a plurality of regions having different propagating bulk wave acoustic velocities are repeatedly provided side by side in a direction in which the plurality of electrode fingers are arranged; In each of the plurality of layers, the plurality of regions are provided from one surface to the other surface facing each other in the thickness direction, and the plurality of regions of one layer and the plurality of regions of the other layer are adjacent among the plurality of layers. and an insulating layer in which at least a part of the region in which the sound velocity of the bulk wave is substantially the same is displaced in the arrangement direction. The plurality of regions of the layer closest to the piezoelectric layer among the plurality of layers are arranged such that each of the plurality of regions overlaps the entirety of one electrode finger of the plurality of electrode fingers in the arrangement direction. 2. The acoustic wave device according to claim 1, arranged repeatedly in the arrangement direction. a temperature compensation layer provided between the insulating layer and the piezoelectric layer, the temperature compensation layer having a temperature coefficient of elastic constant opposite in sign to the temperature coefficient of the elastic constant of the piezoelectric layer;
a distance from a surface of the temperature compensation layer on the insulating layer side to a surface of the piezoelectric layer on which the pair of comb-shaped electrodes are provided is 2λ or less;
the insulation layer has a higher sound speed of a bulk wave propagating than the temperature compensation layer;
3. The acoustic wave device according to claim 2, wherein the layer closest to the piezoelectric layer is in contact with the temperature compensating layer. The acoustic wave device according to any one of claims 1 to 3, wherein the length of each of the plurality of regions in the arrangement direction is 0.5 times or more and 1 time or less the average pitch of the plurality of electrode fingers. . The elastic wave according to any one of claims 1 to 4, wherein the length of each of the plurality of regions in the thickness direction is 0.5 to 4 times the average pitch of the plurality of electrode fingers. device. The plurality of regions of the adjacent one layer have a phase difference of 0.5 to 1 times the average pitch of the plurality of electrode fingers with respect to the plurality of regions of the other layer in the arrangement direction. 6. The acoustic wave device according to any one of claims 1 to 5, arranged repeatedly in a row. The acoustic wave device according to any one of claims 1 to 6, wherein boundaries between the plurality of regions are inclined in a cross-sectional view parallel to the arrangement direction. The plurality of regions are composed of a first region and a second region in which the speed of sound of a bulk wave propagating from the first region is slow,
the second region has a propagating bulk wave speed of 1.01 times or more and 1.1 times or less as compared with the piezoelectric layer;
The acoustic wave device according to any one of claims 1 to 7, wherein said first region has a propagating bulk wave sonic velocity 1.2 times or more that of said second region. A filter comprising the acoustic wave device according to any one of claims 1 to 8. A multiplexer including the filter of claim 9. a support substrate;
a piezoelectric layer provided on the support substrate and being a rotated Y-cut X-propagating lithium tantalate layer or a rotated Y-cut lithium niobate layer;
A plurality of layers provided between the support substrate and the piezoelectric layer, in which a plurality of regions having different propagating bulk wave acoustic velocities are repeatedly arranged in the X-axis direction of the crystal orientation of the piezoelectric layer, are stacked. , in each of the plurality of layers, the plurality of regions are provided from one surface to the other surface facing each other in the thickness direction, and the plurality of regions of one adjacent layer among the plurality of layers and the other layer and an insulating layer in which at least a part of the plurality of regions in which bulk wave acoustic velocities are substantially the same is arranged in the X-axis direction.

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